The present invention relates to hand held manually operated tools and, more particularly, to impacts tools such as hammers and the like having a head structure including two separated members which are joined by an elongated handle structure.
Impact tools such as hammers, axes, picks and other hand held manually operated striking tools are well known and have been used for centuries. Each of these tools come in a variety of shapes and sizes. The specific construction of the impact tool varies widely according to the desired specified use.
Such tools are typically provided with a one-piece head structure formed from steel or the like and usually includes two metallic impact or striking surfaces. Carpentry hammers typically have a metal striking head at one end and a claw configuration at an opposite end. Alternatively, the hammer can include heads formed from a softer material such as lead or hardened rubber material to provide nonmarring impact surfaces.
Hammers typically have included a handle extending away from the head structure to provide the hammer with a generally T-shaped configuration. The one-piece head structure is typically created from a forging operation to add strength to the head structure of the impact tool. Typically, a lengthwise portion of the handle fits through a bore or opening provided in the one-piece head structure. A wedge or other suitable fastening device is driven into the free end of the handle to fasten the handle to the head structure.
When a tool such as a hammer is moved to strike a surface of an object, part of the kinetic energy developed through the hammer""s swing is utilized in doing the desired work on the object being struck, another part is dissipated as heat, while another part is converted into potential energy in the form of recoil or rebound of the hammer from the surface being struck. The distortion of the striking surface of the hammer has potential energy much the same way as a compressed spring. It is this potential energy that causes the hammer to recoil or bounce back from the surface of the object being struck. Moreover, hammers usually transmit some force of the impact to the user""s hand, which will increase efforts and labor of the user, thus reducing the operating efficiency of the tool.
To reduce this problem, there have been developed hammers offering a xe2x80x9cdead-blowxe2x80x9d characteristic. For example, attention is directed to my U.S. Pat. No. 5,408,902, offering a composite hammer embodying a split head design wherein a non-load bearing internal head assembly is carried by a rigid outer load bearing framework which provides strength and stiffness to the tool. The xe2x80x9cdead-blowxe2x80x9d characteristic offered by my patented tool is accomplished through a split head tool design that remarkably reduces and substantially eliminates transference of the impact from the striking head to the user""s hand.
While the invention disclosed in my U.S. Pat. No. 5,408,902 offers significantly improved results over other impact tool designs, there is and industry mandates a continuing effort to improve product technology. As a result of those continuing efforts, the present invention has been realized.
In view of the above, and in accordance with a preferred form of the present invention, there is provided an impact tool including a head structure with first and second members extending in opposite directions from each other but which are maintained in interconnected relationship relative to each other by a handle structure extending normally from and secured to the head structure.
In one form of the invention, the members of the head structure are formed from metal. In that embodiment wherein the impact tool is configured as a hammer, at least one of the members of the head structure is a striking head which can include an exposed metal striking surface. The other member of the head structure for the hammer can be configured as a claw or, alternatively, a second striking head with an exposed metal striking surface.
In a preferred form of the invention, each member of the head structure includes a working portion and an attachment portion. The attachment portion of each member of the head structure extends, at least partially, in surrounding relation relative to a lengthwise portion of the handle structure so as to prevent the member from becoming disassociated with the handle. Forming the attachment portion of a claw-like configured head with a clevis-like configuration appears beneficial to distribute forces imparted thereto during operation of the tool.
The handle structure includes an elongated handle formed from any of a myriad of materials selected from the class comprising; wood, plastic, metal, nylon, fiberglass, an elastomer, or suitable rigid material. In a preferred form, the handle structure further includes a wedge-like member driven into the free end of the handle. The wedge-like member serves to maintain the handle structure and head structure in secured engagement relative to each other.
In accordance with one aspect of the present invention, and while remaining interconnected through the handle structure, the members of the head structure are separated from each other in an axial direction. The spacing between the members of the head structure allows for movement of the head structure members in response to one of the head structure members being struck against a surface. That is, when one member or head of the head structure is struck against a surface, the spacing between the heads or members of the head structure allows the unstruck head to move toward and impact against the struck head thereby providing a secondary blow that inhibits the tool""s struck head from rebounding from the struck surface and thereby dampening vibration through the handle.
In a preferred form of the invention, the attachment portions of the heads or members of the head structure are configured with confronting impact surfaces. The spacing mentioned above is provided between the impact surfaces on the heads or members of the head structure. The range of spacing between the members of the head structure varies and is dependent upon a number of factors. That is, the spacing between the members of the head assembly varies as a function of the mass distribution or geometry of the head structure members, the material from which the head structure members are formed, the timing of the collision between the head structure members, and the length of time the striking surface of the head structure striking member remains in contact with the struck surface. A spacing between the impact surfaces ranging between about 0.010 inches to about 0.070 inches appears appropriate.
To promote movement of the members or heads of the head structure moving toward each other in response to use, the tool of the present invention can further include elastomeric material disposed between the handle of the tool and the heads or members of the head structure. The elastomeric material has a hardness ranging between about 40 Shore A durometer hardness and about a 95 Shore A durometer hardness. Suffice it to say, the elastomeric material acts as a spring for returning the nonstruck head to a normal or operational position after moving toward and impacting with the struck head or member of the head structure. Accordingly, any suitable material which, during operation of tool, will initially compress and subsequently return the unstruck head to an operational position will suffice.
Another aspect of the present invention relates to configuring at least one of the members of the head structure from laminations. The other member or head of the head structure is captively received between laminations of the other member. After captively arranging the heads or members of the head structure relative to each other, the laminations are fixedly secured to each other. The handle of the tool extends through and is maintained in association with either of the members or heads of the head structure and extends generally perpendicular relative thereto.
With this aspect of the present invention, a striking plate or cap can be arranged in combination with the laminations. The striking plate defines a striking surface for the tool and, thus, inhibits separation of the laminations during use of the tool.
With the present invention, the head structure preferably comprises dual heads or members which are generally axially aligned relative to each other. Because the heads or members of the head assembly of the present invention can be manufactured separately, the manufacturing equipment and processes for forming the heads or members of the head structure are significantly simplified, thus, reducing manufacturing costs and thereby enhancing the selling price of the tool. Configuring one or more of the striking heads with laminations furthermore enhances the manufacturing process.
Arranging elastomeric material between the heads and the handle of the tool furthermore enhances this invention. The elastomeric material effectively isolates the heads from the handle and thereby significantly reduces vibration transfer from the head structure through the handle and to the user""s hand.
The concept of splitting the heads of the head structure to allow for axial movement of the heads relative to each other furthermore enhances performance characteristics of the present invention. Thus, when one head or member of the head structure is struck against a surface, the other head or member of the head structure acts as a lagging mass and provides a secondary blow to inhibit the struck head from rebounding from the surface being struck. According, an advantageous xe2x80x9cdead-blowxe2x80x9d feel is provided to the tool. It has been found that vibrations normally experienced in the handle of the tool are not discernable with the tool designed in accordance with the present invention.
Still another aspect of the present invention involves arranging a skin of resin impregnated fiber material, preferably an arimid fiber material, along and about the lengthwise portion of the handle structure extending into operative association with the head structure of the impact tool. Preferably, an epoxy is used in combination with the fiber material or skin. Moreover, the fiber skin or material plus the epoxy defines a more cumbersome path for impact vibrations to traverse between the striking head of the head structure and the handle structure thereby significantly reducing vibration transference during use of the tool. Additionally, a cosmetic cover is preferably arranged beneath the head structure and extends about the handle of the handle structure to aesthetically cover any free ends of the fiber material extending from the head structure of the tool. As will be appreciated from an understanding of this aspect of the present invention, the presence of an epoxy material about that portion of the handle structure extending into operative combination with the head structure will enhance securement of the head structure and handle structure to each other while advantageously dampening vibrations whether the head structure is of a unitary design or of the two piece design as disclosed above.
These and other objects, aims, and advantages of the present invention will become more readily apparent from the following detailed description of the invention, the appended claims, and the accompanying drawings.